[Gigachad]

It's because private communities are the only ones free from mass abuse. Public forums moved to private discord groups with hard to find invite links / etc because public forums take an army of anti abuse workers to keep alive. While a discord group just needs a few people to kick the trouble makers and maybe revoke the invite link for a while.

[throwamon]

If that's the entire problem, then why not make these forums read-only by default (while still keeping them publicly viewable) and hand out invite links as in Discord?

Lobste.rs, for instance, has an interesting "invite tree" concept where your reputation is bound to people you've invited and who they've invited and so on.